Store conversation history in support of multi-turn conversations

[bobjac]

As a user I would like to be able to have follow-up questions to the AI and have the AI be aware of the full conversation history.

Implementation:

• Create an IChatHistory Repository and base implementation that stores ChatMessages. Initial implementation could be in-memory
• When an agent executes, pull the entire chat history based on the thread id, add the latest message to the end of the list and submit the entire chat history to the AI. After receiving a response, add the response to the end of the list and save